Earthquakes & Tsunamis in Tonga

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Earthquakes in Tonga

With Tonga sitting on the zone known as the Pacific Rim of Fire, it is prone to experiencing earthquakes. Most earthquakes occur on the ocean floor, making tsunamis more of an issue than the quake itself (see the section below). However, large earthquakes can still cause buildings to fall, fires and landslides.

Earthquakes That Have Occurred in Tonga

While most earthquakes that occur in Tonga are small tremors with no impact on travellers, larger earthquakes in the recent past have included:

• November 1865 – 8.0 Ms (surface-wave magnitude) earthquake off the coast of Ha’apai which caused minimal damage
• April 1919 – 8.1 Mw (moment magnitude) earthquake between Vava’u and Niue which caused minimal damage
• June 1977 – 7.2 Ms earthquake off the south coast of Tongatapu caused one death and serious damage to infrastructure
• May 2006 – 8.0 Mw earthquake in Ha’apai caused one injury, some damage to infrastructure and landslides
• March 2009 – 7.6 Mw earthquake off the south coast of Tongatapu which caused minimal damage.

What to Do if You Experience an Earthquake in Tonga

There is no way to predict earthquakes, so any actions you take for your own safety have to happen while the earthquake is happening. Measures you can take include:

• If you are in a building, seek shelter under a table, bench or bed. You can also stand under the doorframe which is one of the strongest foundations in a building
• Stay away from windows, mirrors, cupboards and shelves
• Stay out of elevators and stairways
• If you are outside, move away from power lines, trees, buildings and anything else that could fall on you.

For more safety advice, see Is Tonga Safe for Tourists?

(c) tongapocketguide.com

Tsunamis in Tonga

Tsunamis are the largest danger of earthquakes in Tonga, but can also be caused by landslides, volcanic eruptions and anything else that rapidly displaces a large volume of water.

Since 1865, there have been six tsunamis recorded in Tonga, which is quite rare compared to other countries. The most impactful tsunami recorded was in September 2009, which was caused by an earthquake in Samoa. The tsunami hit Niutatoputapu in The Niuas, causing 11 deaths and destroyed villages.

How to Prepare for a Tsunami in Tonga

A little bit of warning is usually given when a tsunami is about to hit land, but tsunamis happen fast and require fast action. There are a few ways you can prepare for a tsunami in Tonga, which include:

• Be aware of tsunami evacuation maps for where you’re staying
• Listen out for tsunami warnings emitted through loudspeakers and sirens in urban areas, through radio, TV, online on news websites and on the Tonga Meteorological Service website.

What to Do if a Tsunami Warning is Issued

Tsunami warnings can be issued through sirens, loudspeakers and through news media in the South Pacific. Other signs of a tsunami could be a strong earthquake, seeing the ocean recede and/or hearing unusual roaring sounds from the ocean. If any of these signs occur, follow the steps that are appropriate:

• If you see signs of a tsunami before a tsunami warning is issued, act immediately
• If you’re on the coast, move to inland and to higher ground
• If you are in a town and can’t move inland, seek shelter in the upper levels of a multi-storey building
• Head to areas as advised on tsunami evacuation maps.

After a tsunami, continue listening to media for announcements. Only move back into the affected areas when authorities have said it is safe to do so.